Evelyn Waugh was born 100 years ago, on October 28, 1903. He does not seem to have died. His complex personality, reduced to a comic grotesque clutching an ear trumpet, struts and fulminates in countless anecdotes. But his real transcendence of death comes in his fiction.

It is ironic that Waugh's rebarbative, bi-polar social persona should dominate his literary reputation. He was quite frank about its fictional nature. It was, he tells us in the manifestly autobiographical Ordeal of Gilbert Pinfold (1957), a self-defensive imaginative construct. "It was his modesty which needed protection, and for this purpose, but without design, he gradually assumed this character of burlesque." The role he cast himself in, Waugh confesses, was a combination of eccentric don and testy colonel, a paradoxical "front of pomposity mitigated by indiscretion, that was as hard, bright and antiquated as a cuirass". He acted the role strenuously till it dominated his whole personality and he could not shake it off. Waugh was well aware how badly he appeared to others. In his madness, Pinfold is persecuted by hallucinatory voices accusing him of snobbery, greed, irascibility, homophobia, homosexuality, anti-semitism, bigotry and bad manners. They were an accurate echo of Waugh's popular reputation, still unchanged today.

Is it surprising, then, to hear of Waugh's modesty needing protection? Modesty is the last thing we'd associate with him. And yet Waugh's estimation of his literary achievement remained resolutely modest throughout his life. Pinfold opens with a short paragraph on the contemporary English novelists, among whom Pinfold "stood quite high", no more than that. "He regarded his books as objects which he had made, things quite external to himself to be used and judged by others." To do Waugh the justice he deserves, we must judge him by his novels, rather than his life. They are why his vibrant personality continues to suffer its phantasmagoric afterlife.

And yet there is an indissoluble link between Waugh's life and art. No writer quarried his own experiences as thoroughly and imaginatively. What is fascinating is the absurd triviality of some of these experiences, and the dazzling invention with which they are selected, refashioned and set in order. Waugh was unabashed about his own techniques.

Early on he openly described them in an article for the Daily Mail, called "People who want to sue me", prompted by the success of Vile Bodies. Coming hard on the break-up of his first marriage, the novel had been glibly misread as a roman à clef. Waugh freely concedes that "there must be a connection of some kind between a writer's work and his life. His knowledge of the world is limited by his experience ... But here the connection ends" - and Waugh's own artistic credo begins:

"If only the amateurs would get it into their heads that novel-writing is a highly skilled and laborious trade. One does not just sit behind a screen jotting down other people's conversation. One has for one's raw material every single thing one has ever seen or heard or felt, and one has to go over that vast, smouldering rubbish-heap of experience, half stifled by the fumes and dust, scraping and delving, until one finds a few discarded valuables.

"Then one has to assemble these tarnished and dented fragments, polish them, set them in order, and try to make a coherent and significant arrangement of them. It is not merely a matter of filling up a dustbin haphazard and emptying it out again in another place."

Scoop best illustrates both the bizarre nature of Waugh's dented valuables, and the exquisite order in which he arranges them - political reversals, mistaken identities, children's stories, typing mistakes, a Latin telegram - all changed, changed utterly.

In August 1935, Waugh was sent to Abyssinia, with 100 or so other journalists, to await its invasion by Mussolini's fascists, once the rainy season was over. He was employed by the Daily Mail, one of only two papers taking a pro-Italian stance.

Waugh's personal life had changed radically. After the end of his first marriage and many years' restless bachelorhood, he was courting Laura Herbert and serenely happy. The annulment of his first marriage was working its way through the Vatican. The Mail gave him a typewriter and on the long sea-journey to Djibouti he learned to type.

In Scoop his inexpertise is happily transferred to William Boot:

"The keys rose together like bristles on a porcupine, jammed and were extricated; curious anagrams appeared on the paper before him ..."

The journalistic assignment was not a success. Five months' close proximity deepened Waugh's loathing of the press. Journalists were "lousy competitive hysterical lying". He missed the one great scoop of the war and his own scoops were dogged with failure. The major story was the involvement of an American-backed British entrepreneur, Francis Rickett - one of several prototypes for Scoop's Mr Baldwin - who aroused Waugh's suspicions on the boat to Djibouti. Rickett's airy name-dropping of the pack he hunted with in the Midlands sounded fishy. And whenever he received telegrams in code, which he often did, he pocketed them saying, "From my huntsman. He says the prospects for cubbin' are excellent." This too is transferred directly to Scoop when William dines on the train to Marseille with the enigmatic Mr Baldwin:

"'I rejoice in the Cote d'Azur. I try to get there every year, but too often I am disappointed. I have so much on my hands - naturally - and in winter I am much occupied with sport. I have a little pack of hounds in the Midlands.'

'Oh? Which?'

'You might not have heard of us. We march with the Fernie. I suppose it is the best hunting country in England. It is a little hobby of mine.'"

Waugh's engagingly amateurish response was to write a letter (not a cable) to Penelope Betjeman to inquire whether anything was known of Rickett among her hunting friends. In fact, Rickett negotiated a vast concession of mineral rights from Haile Selassie - in the terrain to be covered by the Italian advance. It was an ingenious act of self-defence on the emperor's part.

When the Rickett story broke, however, Waugh was out of Addis Ababa on a different trail. A resident Frenchman, improbably named Count Maurice de Roquefeuil de Bousquet, had been working a mica concession in a town called Jijiga. He had been imprisoned with his wife for spying, after a Somali woman was caught leaving his house with a film hidden in her left armpit. That was one story. Within hours, Waugh had also stumbled on secret information about the Abyssinian line of defence.

Neither story was of the least interest to the Daily Mail, whose attention was solely on Rickett.

A similar reversal occurred later. As a fellow-Catholic and, at that time, political sympathiser, Waugh was friendly with the Italians - or "slappers with the Wops", as he put it. In this way, he obtained advance details of the Italian minister's departure from Addis, which he knew signalled the beginning of the Italian invasion. To scoop his rivals, Waugh cabled this exclusive news to his head office in Latin. The Mail thought it gibberish and binned it.

Waugh in Abyssinia (1936), the travel book describing this period, is marked by a pattern of reversal. The journalists' predictions were constantly mistaken, and the book employs an ironic refrain: "How wrong we were!" A story was floated that an American nurse had been blown up in Adowa. Waugh and his colleagues wired back, "Nurse unupblown". It becomes a feature of Scoop : "ADEN UNWARWISE", "UNPROCEED LAKUWARD", "NEWS EXYOU UNRECEIVED".

The Daily Mail sacked Waugh. and in December 1935 he left Abyssinia with relief. On his way home he decided to call on an acquaintance he had met in London. She was the wife of the Counsellor at the British Legation in Tehran. Unfortunately he misremembered her posting - and sent a telegram to the British Ambassador in Baghdad, enquiring, "Would I be welcome if I came to you for weekend Evelyn Waugh". The reply was unenthusiastic: "Fairly. Ambassador". In the summer of 1936, Waugh returned to Abyssinia to observe it under Italian rule. By now, he had lost all his pro-Italian fervour. Only the fascist road-building programme fired him. He flew to Asmara, in the north, where a town originally built for 2,000 now accommodated 60,000 Italian navvies - and what Waugh tactfully describes as "seven unattached white women" provided by the Italian authorities. The women worked from 9 in the morning till 11.30 at night, with a rest every three months. When Waugh was shown the brothel, there were about 80 men waiting for attention. "Feminine company," he drily observed, "is a primary need for Italians. It is a romantic rather than a physical need; the latter, in a rough and tumble way, has been catered for." Not surprising, then, that the telegram announcing the arrival of the ambiguously gendered Evelyn Waugh, should have aroused the Italian press officer in Asmara to a fever of romantic anticipation. He met every possible plane and train. "His friends declared that he had, with great difficulty, procured a bouquet of crimson roses. The trousered and unshaven figure which finally greeted him must have been a hideous blow."

These trivial, miscellaneous experiences shape Scoop. They are not merely transcribed directly, as we have seen. That is the least of their functions. What is much more dazzling is the fantastical structural role they acquire.

In a negative review of Cyril Connolly's Enemies of Promise, Waugh had pointed out that the most important skill of the novelist was "to conceive and complete a structure". The significance of a phrase on one page may owe its significance to another 50 pages distant, and, Waugh adds with icy understatement, "I beg Mr Connolly to believe that even quite popular writers take great trouble sometimes in this matter."

Scoop is a prime example of this. It took Waugh an unprecedentedly long time to write. He began it in October 1936. The first two chapters were written in a fortnight, and deemed by him "light and excellent". In February 1937 he observed with detachment that it "has good material but shaky structure". By July 1937 he decided it had to be "entirely rewritten". It was finally published in May 1938, with the structure well and truly fixed. But most readers are unlikely to be aware of its consummate skill, the "elegance and variety of contrivance" Waugh modestly allowed his authorial alter-ego, Pinfold. The entire novel is elaborately built on a playful pattern of mistaken identities, anagram, metathesis, reversal, transposition and transfiguration.

The pattern is introduced by an arresting cameo on the first page:

"Algernon Stitch was standing in the hall; his bowler hat was on his head; his right hand, grasping a crimson, royally emblazoned dispatch case, emerged from the left sleeve of his overcoat; his other hand burrowed petulantly in the breast pocket ... He spoke indistinctly, for he was holding a folded copy of the morning paper between his teeth.

'Can't get it on,' he seemed to say."

This is a funny muddle of a specific kind. It turns on cross-over: the minister has his hand down the wrong coat-sleeve. Transposition and crossover recur throughout the novel. In the Megalopolitan offices "on a hundred lines reporters talked at cross-purposes". In Ishmaelia, the lost luggage van finally reappears intact - because "mysteriously it had become attached to the special train, had in fact been transposed". The plot turns on two major transpositions. William Boot is mistakenly sent to Ishmaelia instead of John Boot. And on William's triumphal return, Uncle Theodore Boot is persuaded to take William's place at Lord Copper's ghastly celebratory banquet.

Linguistic reversals sustain the pattern in miniature: the novel opens on "a biting cold mid-June morning"; newsboys are selling "the lunch-time editions of the evening papers". Misunderstandings and meta-theses sustain the mode: Mr Salter, at the Megalopolitan offices, has been told to regale William with heavy hospitality and light conversation about country matters - mangold-worzels, and root crops generally:

"There was a pause, during which Mr Salter planned a frank and disarming opening. 'How are your roots, Boot?' It came out wrong.

The novel's interchangeable press magnates, Lord Copper and Lord Zinc - of the Brute and the Beast, respectively - are paralleled by Pip and Pop, the Bedtime Pets, in the Beast's Children's Corner. Later, Pip and Pop are transmogrified into the Popotakis Ping-Pong Parlour at Jacksonville. The game of ping-pong's high-speed ricochet, a to-and-fro getting nowhere, epitomises the novel's elaborately inconclusive narrative structure. In the same ping-pong mode, Ishmaelia has two political parties, the CumReds and the White Shirts - comic travesties of Communist comrades and Fascist blackshirts. They are diametrically identical, indistinguishably opposed.

"'I gather it's between the Reds and the Blacks.'

'Yes, but it's not quite as easy as that. You see, they are all Negroes. And the Fascists won't be called black because of their racial pride, so they are called White after the White Russians. And the Bolshevists want to be called black because of their racial pride. So when you say black you mean red, and when you mean red you say white ...'"

Even Mr Salter is confused here. The CumReds are black, so "when you say black you mean red". But the Fascists are White Shirts, so the next phrase should run, "and when you mean black [not 'red'] you say white". The point is not just that they are indistinguishable, but that propaganda makes black seem white - a simplifying gloss implied but withheld by Waugh when William hears the orators of both sides. At Hyde Park, the Ishmaelian Marxist claims that all whites are really black ("Who built the Pyramids? A Negro. Who invented the circulation of the blood? A Negro ..."). At his makeshift embassy, the fascist maintains that all blacks are really white ("As you will see for yourself, we are all pure Aryans. In fact we were the first white colonizers of Central Africa").

On his return to Abyssinia in 1936, Waugh confessed that "it was fun being pro-Italian when it was unpopular. I have little sympathy with those triumphant fascists now." Scoop is not a political novel. Rather, it is, as Waugh noted in his dairy, "light and excellent". Its lightheartedness is epitomised by its two major literary sources. One structural cross-binding delicately securing the novel's three-part structure is Beatrix Potter's Tale of Johnny Town-Mouse, which begins:

"Johnny Town-Mouse was born in a cupboard. Timmie Willie was born in a garden. Timmie Willie was a little country-mouse who went to town by mistake in a hamper."

Book One revolves around William Boot's apprehensive journey up to town, away from his secure country nest. At this point, John Boot, his sophisticated metropolitan cousin, is a self-evident Johnny Town-Mouse. In Book Three, his role passes to Mr Salter, reluctantly forced out of frenetic, familiar London into the bucolic terrors of Boot Magna. Waugh's other major source is the fairy tale, Beauty and the Beast. It haunts the text in the premonitory pairing of the rival papers, the Brute and the Beast. It emerges into full daylight at William's triumphal return to London as BOOT OF THE BEAST. William is the Beast-transfigured from dud cub reporter to the cynosure of Fleet Street (the very reverse of what happened to poor, sacked Eve lyn). Yet Waugh specifically did not want to end the novel on this high note. He was insistent that Boot should return home without ambition ever to leave again. Like Timmie Willie, William returns happily to the total obscurity from which he came.

The novel ends where it began. The maze of its narrative confuses the reader as much as its cast. In the last pages, a vinous optimism descends. Happy endings abound, as befits a fairy-tale - a happy ending for Uncle Theodore, with his shady London chambers and feline prowlings after dark; a happily dull ending for Mr Salter as Editor of Home Knitting; a happy anticlimactic ending for William, safe at home in Boot Magna, composing Lush Places once more. "The waggons lumber in the lane under their golden glory of harvested sheaves, he wrote; maternal rodents pilot their furry brood through the stubble ..."

Waugh, however, was a realist. The novel ends on a chillier note: "Outside the owls hunted maternal rodents and their furry brood." It was 1938. War was on its way.

· Ann Pasternak Slater is a Fellow of St Anne's College, Oxford. She has written the introduction to the new Everyman's Library collection of Black Mischief, Scoop, The Loved One, The Ordeal of Gilbert Pinfold .